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AD9361 - PRBS for quadrature

Question asked by bornruffians on Jul 13, 2016
Latest reply on Jul 13, 2016 by bornruffians

I can't figure out how the Quadrature (Q) component is populated when BIST PRBS is enabled on AD9361.


This post describes the BIST PRBS algorithm:

Exact HDL implementation of AD9361 PRBS

Each successive value is this: dout = {din[14:0], ((^din[15:4]) ^ (^din[2:1]))};


I've confirmed that this works for the In-Phase (I) component, but it appears something else is done for Q.


At any sample, I noticed that bits 7:0 for Q are the bit-reverse of bits 7:0 for I.  Maybe that's just coincidence due to the PRBS.


If someone can explain how to compute/check Q for the BIST PRBS, that'd be great.  Thanks